The present invention relates generally to a signal generator capable of producing a plurality of control signals and a sensing circuit for detecting the control signals produced by the signal generator. Even more particularly, the invention relates to signal generators that can be produced at low cost.
Remote signal generators capable of sending command signals are known. FIG. 1 shows an electric lamp wall box dimmer 12 coupled to a remote signal generator 10 through two conductors 14 and 16. A wallbox dimmer and remote signal generator are available from the assignee of the present application and known as the Maestro dimmer and accessory dimmer. The wall box dimmer comprises a signal detector 32 capable of receiving and decoding three discrete signals generated by the signal generator 10. The signals are generated when a user actuates momentary contact switches xe2x80x9cTxe2x80x9d, xe2x80x9cRxe2x80x9d or xe2x80x9cLxe2x80x9d. The xe2x80x9cRxe2x80x9d switch generates the signal shown in FIG. 2A when actuated which causes the dimmer to increase the light intensity of the coupled load 20. The xe2x80x9cLxe2x80x9d switch generates the signal shown in FIG. 2B when actuated which causes the dimmer to decrease the light intensity of the coupled load 20. The xe2x80x9cTxe2x80x9d switch generates the signal shown in FIG. 2C when actuated which causes the wall box dimmer 12 to turn on to a preset light intensity, go to full light intensity, fade off slowly or fade off quickly. Each time the switch xe2x80x9cTxe2x80x9d is actuated, the signal generated and sent to the signal decoder 32 is always the same. To cause the dimmer to react differently to the closure of switch xe2x80x9cTxe2x80x9d, the user must actuate the xe2x80x9cTxe2x80x9d switch differently. When a user actuates switches xe2x80x9cRxe2x80x9d, xe2x80x9cLxe2x80x9d or xe2x80x9cTxe2x80x9d the signal detector 32 actually receives a string of signals because the user is usually not capable of actuating and releasing the switches in less than one line cycle (16 mSec on a 60 Hz line). The signal is only generated as long as the switch is closed.
A microcomputer 28 in the wall box dimmer 12 is capable of determining the length of time the switch xe2x80x9cTxe2x80x9d has been actuated and if the switch xe2x80x9cTxe2x80x9d has been actuated and released a plurality of times in quick succession. The microcomputer is programmed to look for the presence or absence of an AC half cycle signal from the signal detector 32 a fixed period of time after each zero cross of the AC line, preferably 2 mSec. The microcomputer only looks once during each half cycle. The advantage of the signal generator of the prior art is its low cost. The drawback to this type of signal generator is that there are a limited number of signals that can be generated without requiring the user to actuate the same actuator repeatedly or actuate the actuator for an extended period of time in order to perform additional functions. Details of a signal generator according to the prior art are disclosed in issued U.S. Pat. No. 5,248,919, the entire disclosure of which is hereby incorporated by reference. There is a need for a low cost signal generator that does not require the user to actuate the same actuator in different ways to initiate multiple functions.
Also known are phase control lamp dimmers which use a semiconductor device to control the phase of an AC waveform provided to an electric lamp thereby to control the intensity of the lamp. These phase control dimmers are not ordinarily considered to be signal generators of the type contemplated herein. Further, such phase control dimmers, until turned off, produce a phase shaped AC waveform continuously unlike the signal generator described above in connection with FIG. 1.
Other signal generators of the prior art can generate a plurality of control signals, but require a microprocessor in the signal generator which converts the actuator actuations into digital signals for processing by another microprocessor. The drawback to this type of signal generator is the added cost of the microprocessor and its associated power supply.
Accordingly, there is a need for a low cost signal generator that overcomes the drawbacks of the prior art.
It is an object of the present invention to provide a signal generator which is capable of producing a plurality of different control signals.
Yet still a further object of the present invention is to provide a signal generator which can be manufactured at low cost.
It is yet still a further object of the present invention is to provide a signal generator which produces unique control signals based upon portions of alternating current waveforms.
Yet still a further object of the present invention is to provide a sensing circuit for detecting the control signals produced by the signal generator circuit according to the present invention.
Yet still a further object of the present invention is to provide a signal generator which requires only two wires for connection to a sensing circuit.
The above and other objects are achieved by a signal generator comprising a switch in series with at least one of a zener diode and a diac, the signal generator producing an output when the switch is actuated, the output having a region where the current is substantially constant.
The above and other objects are also achieved by a signal generator comprising at least one of a zener diode and a diac, the signal generator producing an output when a switch in series with the at least one of a zener diode and diac is actuated, the output having a region where the current is substantially constant.
The above and other objects are also achieved by a signal detector circuit coupleable to an AC source comprising a sense circuit, and a control circuit, the control circuit producing a signal when the sense circuit receives an AC signal having a region where the current is substantially constant.
The above and other objects are also achieved by a signal generating circuit coupled to an AC supply, the circuit comprising at least one first switch device coupled to the AC supply, at least one triggerable switch device coupled to the first switch device; operation of the first switch device causing said triggerable switch device to trigger in response to the AC supply at a predetermined voltage, thereby providing at least a portion of a waveform of the AC supply as a control signal and wherein the control signal terminates within a predetermined period of time after operation of the first switch device terminates. The triggerable switch device can be a zener diode, a diac or may be a semiconductor switching device having a control electrode, e.g., a triac, SCR or transistor, or an opto coupled version of such switching devices.
The above and other objects are also achieved by a circuit for sensing one of a voltage and current from a signal generator circuit producing a plurality of unique control signals based on an AC supply voltage, the sensing circuit comprising a detector detecting one of a voltage level and current level in a line coupling the sensing circuit and the signal generator and producing a sensed signal; a controller for causing said detector to detect one of the voltage level and current level at a plurality of times in a half cycle of the AC supply voltage; the controller providing a control signal based on the sensed signal.